The general principle of solar thermal technology is based on the concept of concentration of solar radiation to heat a heat transfer fluid and generate electricity.
Solar energy collection and its concentration is one of the greatest challenges in the development of solar thermal plants. There are mainly two types of technologies of concentrators: spot concentration and linear concentration. Linear concentration is easier to install because it has fewer degrees of freedom, but it has a lower concentration factor and therefore reaches lower temperatures than spot concentration technology.
Within spot concentrators, parabolic disc concentrators and the tower or central receiver power plants can be distinguished. Within the linear technology, there are the Parabolic Cylinder Concentrators (PCC) and the new Fresnel-type Linear Concentrators (FLC).
Both the central receiver power plants and the FLC require a field of heliostats to capture and concentrate solar power.
A heliostat consists of a panel with a surface of 40 to 120 m2 consisting of a set of mirrors that are on a frame. Each mirror unit with its frame unit is called a facet. The set of all these facets is what will be later mounted on the mobile structure of the heliostat (trusses, arms and actuation).
Usually, this structure has solar tracking by two movements, azimuthal and elevation, so that the reflected rays reach at all times a focal point located at the top of a tower in which the receiver is located. A heat transfer fluid circulates through the receiver from which electrical energy is produced.
To concentrate solar radiation these reflecting mirrors are slightly curved, the radius of curvature being one of the critical optical characteristics in the manufacture of the same, to direct sunlight correctly with great precision to the receiver.
According to the distance to which the receiver is placed, mirrors have a certain curvature. To achieve the highest performance possible, the curvature parameters of the mirror surface must be respected as closely as possible.
It is of vital importance to develop resistant, reliable heliostats with high optical quality and at a low cost to achieve a feasible solar thermal plant, since the heliostat field is responsible for approximately half of the total cost of these power plants.
That is why there is a tendency to manufacture heliostats of large surface area and to use mass production, to be able to reduce the manufacturing costs to the maximum.
Thereby, any system or invention that achieves simplifying the assembly and manufacture of these mirrors, as well as increasing strength and reliability, is a very important progress for this type of technology.
One of the manufacturing systems of facets that has been used until now consists of binding with adhesive a mirror to a carrier construction. This involves taking the flat mirror and placing it on a carrier surface that has the desired curvature, spreading adhesive and placing an outer annular frame or some form of fixation thereon to remain until the adhesive hardens. If the curvature to which the mirror has to be subjected is very sharp, thermal forming procedures are used in addition.
This solution is very expensive because the carrier structure must meet the exact requirements of precision outlined above.
An alternative to try to reduce costs that is known is the manufacture of a mirror without such precision and carrying out the precision adjustment subsequently (CA2237882A1). Therefore defining in the carrier structure the different points where the adjustment screws will be introduced is necessary. This procedure needs a high quality of the materials used in the carrier structure as well as employing specialized personnel for the adjustment.
Therefore, the present invention is intended to provide a procedure for the manufacture of facets and more specifically developing a securing system of mirrors to the structure that facilitates the assembly of the same, does not entail loss of precision, and yet improves properties and allows a low-cost mass production.